The present invention relates to an apparatus and method for performing ophthalmic orbital surgery, and more particularly, to a method and apparatus for performing minimally invasive ophthalmic orbital surgery using a flexible endoscope. Further, the present invention is related to a method and apparatus for performing minimally invasive ophthalmic orbital surgery using an image guided navigation system.
Endoscopy has had a tremendous impact on nearly all surgical subspecialties with the notable exception of ophthalmology. This technique began emerging when Kelling performed animal model experimental laparoscopic procedures in 1902. Therapeutic uses of endoscopy were primarily confined to gynecology until 1989 when laparoscopic cholecystectomy was introduced. Endoscopy was technically limited until the development of a video computer chip that allowed magnification and visualization of the images on a video monitors. Endoscopes currently have a wide variety of surgical applications including minimally invasive surgery in orthopedics, gynecology, otolaryngology general surgery, plastic surgery, urology and neuro-surgery. Many of these subspecialties have journals devoted specifically to endoscopic surgery. Ophthalmic applications of endoscopy have included microendoscopic ablation of the ciliary processes and other intraocular interventions. Oculoplastic surgeons currently use rigid endoscopes for small incision brow lifts and dacryocystorhinostomies. There are few reports in the literature regarding the use of endoscopes in the orbit.
The retrobulbar space remains one of the least approachable spaces in the human body. An orbitotomy, either through a medial approach disinserting the medial rectus or a lateral approach removing the zygoma and more recently through a superomedial lid crease, is the most common surgical approach to the optic nerve. Although the concept of using an endoscope in the orbit has been explored, endoscopy has not gained acceptance for intraorbital use.
An orbital endoscope was designed in the late 1970s by Norris and Clearsby. A rigid 1.7 mm diameter endoscope was developed with a lens, a 2.2 mm cannula with irrigation conduit, a 2×3 mm cannula with side port for instruments and a fiber optic ring surrounding the waveguide for intraocular surgery. Drs. Norris and Clearsby then used their endoscope in fifteen patients. They used saline to visualize the orbit which led to swelling of the tissues which decreased the endoscopic view. They noted problems of deep orbital bleeding, and pressure within the orbit from infusion of irrigating fluid. In addition, they noted that using air was not successful for visualization. Norris later refined his technique to biopsy orbital lesions for cytological analysis. Again he noted the problem of not being able to control bleeding. See Norris, J., Stewart, W., “Bimanual endoscopic orbital biopsy,” Ophthalmology, 1985. In discussion following Dr. Norris' 1985 article, Dr. Robert Waller noted that this technique would be helpful in distinguishing between optic nerve tumors.
More recently, the Olympus HYE flexible endoscope has been used to explore the orbit in four live dogs. Hyaluronic acid was used to visualize the tissues. There has been at least one abstract report of a flexible endoscope used to perform optic nerve sheath fenestration in a cadaver.
The Free Electronic Laser (FEL) is an infrared research laser that has significant advantages over conventional lasers. Conventional lasers are limited by collateral damage and potential photochemical effects. The FEL operates at non-photochemical single-photon energies which are tunable to the vibrational modes of proteins, lipids, or water. The FEL is tunable between 2 and 9 μm with a 5 μsec macropulse structure consisting of a train of picosecond pulses spaced 350 psec apart. Wavelengths corresponding to specific molecular absorption peaks may be selected for investigation. There are presently about five free electron lasers (FELs) in the United States. Duke University houses a free electron laser studying applications in the UV range. Vanderbilt University houses one of the three tunable FELs in the United States. Vanderbilt University presently has the only FEL facility approved for human use. The Vanderbilt University FEL has been used in the 2.8-10 μm infrared spectrum. Other centers have reported using the FEL in corneal tissue. Tissue ablation at the “amide 11 band” has also been reported. A 6.45 μm (amide 11 band) wavelength has been previously experimented with in optic nerve sheath fenestration.
Optic nerve sheath fenestration has been performed through a medial orbitotomy with the FEL both in animal models and in humans undergoing enucleation. Some of these studies have been presented in abstract form and others are in preparation.
By utilizing the FEL with an endoscopic delivery system, patients would potentially benefit from minimally invasive surgery. Endoscopy has been shown in other specialties to reduce tissue trauma, improve visualization, and reduce both complications and operative time. Orbitotomies often require retraction on delicate neuro-ophthalmic tissues with the possible complications of optic nerve compression with consequent visual loss, cranial nerve palsies, and injury to the globe or ciliary ganglion. To achieve control of the orbit, extra-ocular muscles may need to be disinserted from the globe or bone may need to be removed. Removal of the surrounding bones of the orbit can sometimes requires a neurosurgical craniotomy to access the posterior orbit. The associated surgical risk is substantial and could be reduced with a minimally invasive procedure. In addition to the technical challenge of surgically approaching the orbit through a standard orbital technique, perioperatively patients are treated with steroids to reduce the incidence of optic nerve injury. Even short term immunosuppression with steroids can allow reactivation of latent viruses and other systemic effects. Less invasive, less traumatic orbital surgery could eliminate the need for perioperative steroid use.
The medial orbitotomy procedure requires disinserting the medial rectus and rotating the globe laterally. Possible optic nerve damage may result from a stretch injury from the lateral rotation or compression from the surgical retractors. Other postulated mechanisms of nerve injury include optic nerve ischemia vasospasm, or post-operative edema. A review of surgical outcomes in 31 patients who underwent Optical Nerve Sheath Fenestration (ONSF) showed that 40% had complications. Those patients who had previous ONSF were more likely to have a visually compromising vascular complication. In isolated case reports, two patients are described who developed total blindness following optic nerve sheath fenestration. One of these patients recovered to 20/30 over three months with only five degrees of vision and the other recovered to 20/800. Spoor reported that one ONSF post-operative death 8 hours following surgery; this death is further detailed’ in an editorial by Keltner to have possibly have occurred from an arrhythmia. Corbett et al. noted a two-week postoperative death in an eighteen year old thought to be secondary to a pulmonary embolus. Decreasing the operative morbidity by reducing the surgical time, anesthetic and traction in the orbit would possibly avoid these complications and is therefore a desirable goal.
The theoretical value of using a laser through an endoscope has been recognized in the past. CO2 noncontact and YAG tipped contact lasers have been advocated and used through traditional oculoplastic approaches to excise lymphangiomas, capillary hemangiomas and applied in patients with coagulation abnormalities. Orbital surgery involving vascular lesions is typically avoided because of the risks of intra-operative bleeding; conservative management of these lesions has thus been advocated in the literature. Occlusion amblyopia and significant physical deformity are recognized indications for undertaking the significant orbital risk. Intra-operative blood transfusion is sometimes necessary. Orbital lymphangiomas can be particularly difficult to excise because of the infiltration of the lesion into the normal orbital structures. Alternatives to excision of these lesions have included direct injection of medication such as steroids, sodium tetradecyl sulfate or OK-432.
A safer, more effective method to excise or medically treat these lesions may be possible with an orbital endoscope, and therefore, an endoscope which can be used effectively in orbital surgery is desirable.
For over fifty years, diagnostic images have been used for surgical guidance, especially in the field of neurosurgery. Image-guided surgery implements two fundamental ideas: first, the concept of an image-space to physical-space mapping or registration, and second, the use of an extracranial device for accurate surgical guidance without direct visualization. Such ideas gave birth to stereotactic neurosurgery, a technique for locating targets of surgical interest within the brain relative to an external frame of reference. This is traditionally defined as the temporary attachment of a mechanical frame to the skull or scalp in order to define a three dimensional (3-D) frame space around a patient. With the advent of computed tomography (CT), the coordinates of a target (i.e. tumor) in image space could be assigned coordinates in frame space if the CT images are obtained with the attached frame. Unfortunately, frames are uncomfortable to patients, must be applied prior to imaging, and are cumbersome in the imaging environment and the operating room.
These factors led to the development of frameless stereotactic surgical systems, or interactive, image-guided surgery (IIGS) systems. In traditional IIGS systems, present surgical position is tracked during an operation and displayed on pre-operatively obtained tomographic images. As the surgeon changes the current surgical position, displayed images are updated in real time. In one of the earliest IIGS systems, physical space surgical position was determined using articulated arms. The position of an articulated pointer was calculated using a personal computer (PC) and overlayed on tomographic images. Magnetic resonance images (MRI) and CT negative films are scanned into the computer and displayed as images on a video interface. Other early image-guided surgical systems also used electromechanical 3-D coordinate digitizers to indicate present surgical position on various representations of patient data, including 2-D transverse, coronal and sagittal CT or MRI slices, and on image renderings of the physical object surface. Since it was necessary to have computers capable of managing large volumes of image information (>100 Mbytes) and updating the display quickly, most early IIGS systems are were developed with VME bus devices running UNIX.
Early IIGS systems were developed on PCs using multiple processors. In a task-oriented asymmetric multiprocessing (TOAM) system developed in 32 bit extended DOS, discrete tasks such as physical space localization, data fetching, and display were conducted asynchronously on specialized processors which communicated with inexpensive, general purpose processors that worked as loaders and schedulers. For physical space localization, several articulated arms with six degrees of freedom were first developed. These cumbersome arm devices were eventually replaced with lightweight cylindrical pen-like probes which could be tracked more easily in the operating room using an optical triangulation system. The spatial location of the guidance instrument was determined using a collection of discrete processors which continually update the physical space location. This location was then passed to the central processor where it was mapped into image space. Once the image space map was complete, the appropriate tomographic slices were selected and displayed. Because this system was designed before the advent of large memory availability, image display relied heavily on hardware manipulation using disk controllers to load images directly from the hard drive. Control of the bus was passed from the main processor to the disk drive controller, where the correct image was fetched and sent to the display processor.
With the continuing increase in performance to price, processes which could only be performed on workstation class machines can now be performed on PCs. An operating room image-oriented navigation system (ORION) was developed in Windows NT using MS Visual C++ 6.0 with the Win32 API. The ORION system was designed to be faster than previous systems, but it was not necessary to redesign the software with each hardware advance. Components of the system were developed as dynamic link libraries (DLLs), so that new technology could be incorporated into the system without a complete software rewrite. The system is also somewhat portable. It runs adequately on any PC with a 200 MHz or higher Pentium processor and 128 MB of memory which also has the appropriate video card and 3-D localizer hardware and software.
When designing an image-guided surgical system, it is desirable that the precise location of an instrument used to perform image-guided surgery be determined on a continuous basis (e.g., update rates approaching 30 frames per second). Further, in an effort to ensure precision, it is desirable to continuously and accurately track the tissue being operated on during surgery. It is desirable to provide such an image-guided surgical system to track endoscopes and associated instruments during ophthalmic orbital surgical and/or investigative procedures.